Carrier transmission



Mardi 21, 1939- J. c; WALTER CARRIER TRANSMISSION Filed June 9, 1936'Patented Mar. y21, 1939 CARRIER TRANSMISSION John C. WalterQEastOrange, N. J., assignor to Wired Radio, Inc., New York, N. Y.,- acorporation of Delaware' A'ppucsuan June 9, 193s, serial No. 84,242

4 Claims.

` This invention pertains in general to the transmission of programs,and specifically relates to a system of the suppressed carrier frequencytype. l

The principal object of my invention consists in providing a signallingtransmission system of the suppressed carrier frequency type havingmeans for transmitting an auxlliarycarrier frey quency as a modulationside band for reception l() at a remote receiving point in connectionwith a carrier frequency replacement operation at said remote receivingpoint.

Another object of the invention comprises providing a transmissionsystem for simultaneously transmitting modulation energy correspondingto intelligence signals and to carrier frequency oscillations. if..

A still further object of the invention consists in providing anarrangement for producing a multiplicity of harmonically relatedoscillation frequencies and modulating one of said frequencies with acarrier frequency for transmission to a remote reception point for useat said reception point in combination with other received frequencies.

These and other objects will be apparent fromv band and transmitted to aremote point of reception,` at which point an auxiliary carrier irel 40quency is combined with received single side'band high frequency energyto audibly reproduce a received signal or program.

It is a feature of the invention that the auxiliary carrier frequency isutilized to modulate so as toproduce modulated high frequency .energyhaving side band modulation, which modulation corresponds to the desiredauxiliary carrier frequency. Upon reception, the carrier -modyulatedfrequency energy is demodulated to produce a base frequency for' carrierreplacement purposes at the point of reception. 'This base frequency isthen utilized to control an harmonic generator to produce aplurality ofharmonically related carrier frequency oscillations of differ- 'highfrequency oscillations of a higher frequency ent frequencies suitablefor combination with the received program modulated high frequencyenergy with carrier suppressed to reproduce the original programmodulation.

Referring to the drawing in detail, power lines 5 I extend from powerequipment 2 in substation 3 andf represent a commercial powerdistribution network supplying three-phase cycle alternating current atsuitable voltages. A master oscillator 4 is provided for producing highfrel0 quency oscillations of a base frequency, which, by way of example,may be 13 kilocycles. The oscillator 4, as well as other umts describedin this specication, comprise electrical organizations known in theradio art for producing the l5 desired and described results. "As anillustration, the master oscillator! may include crystal controlledelectron tube oscillation circuits generating the desired frequency.

The master oscillator l operates into an hair- 20 monic' generator 6.The harmonic generator 6 produces several desired carrier frequenciessuch as 26 kilocycles, 39 kilocycles, 52 kilocycles, and '18 kilocycles,respectively available over the connections 1, 8, 9 and I0. Theconnections 'I ex- 25 tend to a modulator ampliiler II. The modulatoramplifier II; comprises means including suitable electron tube circuitsfor producing amplified three-phase high frequency energy having acarrier frequency of 26 kilocycles modu- 30 lated by modulation energyderived from Athe program source I2. Such a three-phase system is shownin Patents Nos. 1,622,135 and 1,730,412, is. sued to Robert D. Duncan,Jr. The output of the modulator amplier II, however, operating 35through filter I3, is limited to a single side band with the carrierfrequency suppressed. The output of the filter I3 then operates throughcapaci tlve couplings Il to impress the resultant threephase single sideband carrier suppressed high 40 frequency energy upon the power networkI. Connections 8 and 9 supply their respective car- -rier' frequencyoscillations to other modulator carrier frequency of '1s moeycles ismodulated by 5'5 the base frequency of 13 kilocycles supplied over theconnections I from the master oscillator 4. 'Ihe modulatorampliiier I8,asin the case of the modulator amplifier I I, generates threephasemodulated high frequency energy which,

directed through 'a filter I1, impresses threephase modulated highfrequency energy upon the lines I. It will be seen that the lines Icomprise a transmission medium carrying several bandsof modulated highfrequency energy originated about harmonically related carrierfrequencies which have been suppressed for transmission purposes.

. ically related carrier frequencies corresponding' The power lines Ioperate through a power )transformer I9 vto supply commercialalternating current as well as high frequency energy to, the receivingcircuits'ntained within the consumers premises 20. The transformer I9supplies consumers voltages to the consumers network which include power.connections'extending to the consumers receiver 2|, a demodulator 22,and

frequencies supplied over connections 1, I or I.

The lter 26 selects frequencies within the range. of the carrierfrequency of the oscillations supplied over the connection I0, which, inthe present instance,- is 78. kilocycles. -The output of the iilter 26operates into a demodulator 22 which demodulates` the received. energyto reproduce the base frequencyenergy'supplied over the connections I5.Thisbase frequency` is fed into the harmonic generator 23 which. thengenerates, from the .base frequency, a plurality of harmonto the carrierfrequencies originally available over,

the connections 'I, 8 and). These frequencies are suppliedoverthe'connctions 21, 28 and 2lto a selector switch 3l which, connectedwith the receiver 2 I supplies the necessary carrier frequency to becombined withthe selected modulation side l' band energy, received fromthe lines I, so as toreplace the suppressed carrier and reproduce theoriginal modulation.

Although a preferred form of carrier appreciated that'.v lj variouschanges and equivalent forms can be pro-1A duced without departing fromthe intended scope v has been disclosed, it will be of the invention.Iherefore, I do'not desiieto limit myself to vthe foregoing except aspointed out in .the appended claims. 1.

vWhatI claimas new and desire to secure Letters Patente! the Unitedstaten' isz. 1. A' ton system compxisingfasource of base frequencytions,aphirality of transfrequency ranged. a further fortrans- =mittingacarrler frequency havingiaidinerentmitters controlled Y harmonicsofsaid tions or procimiiii'zv 'inoculated frequency- `energy. with carrierfrequencies 'transmitters'. to v harmonic relationship-with said 'base'means for modulating said carrier frequency uni 'means forsaidfrequencies from lsaid or side-'bends resulting fromid mm flrstmentioned transmitters as well asfrom said further transmitter, andmeans for generating replacement carrier frequencies from the energyreceived from said further tansmitter and combining the same with thesuppessed carrier energy received from said first mentionedtransmitters.

-to reproduce selected signals.

2. A transmission system comprising, a source plied with saidnarmonicany' related carrier rrequencies, means for modulating certainof said.. carrier frequencies with programenergy to pro-v ducemodulatedhigh frequency energy with suppressed carrier, means for supplyinganother of' said modulator ampliers with said base frequencyoscillations asmodulation energy so as to produce therefrom a carrierfrequency having side band modulation energy corresponding to said,

base frequency, a remotely situated receiver for vselectively receivingsaid modulation energy frequencies with carriers suppressed, ademdulator for receiving said carrier modulated high frequency energy,and an hannonicgenerator opv erated by said demodulator for supplying tosaid receiver for replacement purposes azplurality of carrierfrequencies harmonically related )with said traon and reception basefrequency.

3. The method of which comprises generating oscillations at a basefrequency,deriving therefrom 'a group of car-l riers which are relatedto said base frequency, modulatingfat' least one of said carriers byprogram energy, suppressing carrier and one of the side bands resultingfrom said modulation and .transmitting one sideA band-thereof over asuitable medium, modulating-another of said carriers by said vbasefrequency oscillations and transmitting the same over said medium,

receiving said transmissions at al distant point, demodulating the`received carrier to obtain the base frequency, deriving therefrom anharmonic frequency corresponding to the said suppressed carrier, andcombining said harmonic frequency with the received single side band toreproduce its V program.v

4. In a system for transmitting and receving high frequency `energy inthe form of -sidevbands having their carriers suppressed, themethod of.providing suc'h carriers at the 'transmitter and replacing them at thereceiver which comprises,

monies thereof' for carriers, respectively' modu- `latingcertainofsslidcarriers by programs, sup.-

generating a base frequency and deriving harpressing the carriers and.one side band'of each i tion, modulating a different of the basefrequency by said base ting theother side bands of the Vrim togetherwith said bese frequency ned i -lectedlone of said harmonicswith thecorrespond- Jouir ofwanraa.

Iugjreceived side to carrier 7i) der control voi. said base`frequency',receiving .71 f'

